Cylinder of two-stroke internal combustion engines



May 29, c SCHAER v 1,960,597 CYLINDER 0F TWO-STROKE INTERNAL COMBUSTIONENGINE Filed Ja.:n..5, 1952 2 Sheets-Sheet 1 v wmmw m V Fw- W /JW -rruRN 5% May 29,1934. HA'ER I 1,960,597

CYLINDER OF TWO-STROKE INTERNAL COMBUSTION ENGINE Filed Jan. 5. 1932 2Sheets-Sheet 2 I N\/ENTE] 35 and Patented May 29, '1934 oYLiNnE'It orTWO-STROKE INTERNAL COMBUSTION ENGINES Charles Schaer, Langenthal,Switzerland; as-

signor to the firm of 'Sulzer Frres Societe Anonyme, Winterthur,Switzerland Application January 5, 1932, Serial No. 584,807

In Switzerland January 7, 1931 Claims.

This invention relates to cylinders of twostroke internal combustionengines of the kind having admission and" exhaust ports controlled bythe piston, the admission ports being arranged 5 in the cylinder wallsubstantially opposite to the exhaust ports.

It has hitherto been proposed to provide a two stroke internalcombustionengine cylinder with elongated admission ports extending in a spiraldirection in the cylinder wall, the admission was sages leading to theseports being so inclined that the gases i. e. air issue from each portinto the cylinder on a path which, when projected on to the cylinderwall, is substantially parallel to the 5 length of the port.

According to 'the present invention the admission passages whichterminate in the spirally arranged elongated ports are so inclined thatthe air enters the cylinder through each port along a path which, whenprojected on to the cylinder wall, lies ina direction substantially atright angles to the length of the port.

Two constructions of cylinder according to the.

Figure 2 shows a development of the admission 30 ports shown in Figure1,

Figure 3 is a section on the line III-III of Figure 2,

Figure 4 is a view similar to Figure 2 of a modified arrangement of theadmission ports,

Figure 5 illustrates the invention as applied to a double-actingtwo-stroke engine.

In the construction illustrated in Figure 1 the combustion chamber 1is'bounded by the cylinder head 2, piston 3 and liner 4, the cylindercasing 5 being connected at one side to an air receiver 6 and at theother side to an exhaust pipe 7. The air receiver 6 communicates withadmission passages 8 in the cylinder wall through an inter- 5 mediatechamber 9, non-return valves 10 being arranged as shown between thechambers 6 and 9. In accordance with the present invention the admissionpassages 8 terminate in elongated ports in the cylinder wall as shown,thelength or each port extending in a spiral direction while'the walls11 boimding each of the passages 8 are so inclined that the air entersthe cylinder through ,the corresponding port along a path which, whenprojected on to the cylinder wall, lies at right 5 anglesto the lengthof the port; Thus the main body of the air will enter the cylinderthrough each admission port in a path whose projection on the cylindercorresponds to the vector R (Figure 2) which can be resolved .into avertical component X and a tangential component Y.

In Figures 2 and 3 the admission ports are arranged in two sets, one seton each side of a central dividing wall 14. Each port in one set extendsin a spiral direction which is at a substantial angle to that of theports in the other set, whilst in addition the walls 11 bounding eachpassage are inclined at an angle a (preferably between 30 and 45) with aplane tangential to the cylinder. The angle of inclination of thepassages are similar for each set of ports on either side of thedividing wall 14 but the'passages in one set are inclined at an angle tothe passages in the other set. Exhaust ports 14, formed by dividingwalls 13 arranged in the usual manner, are disposed in the cylinder wallsubstantially opposite to the admission ports. 1 The walls 11 arepreferably stream-lined as shown in Figure 3, the central wall 14serving as a guide for the piston rmgs.

The admission ports are so arranged that when the piston moves outwardson its expansion stroke, before beginning to uncover the exhaust ports12, the piston begins to uncover the admission ports, whereupon thecontents of the cylinder expand into the intermediate chamber 9, thenon-retum valves 10 preventing the gases from passing into the receiver6. As soon as the piston uncovers the exhaust ports 12 the cylindercontents will escape through the exhaust pipe 7 whereupon scavenging ofthe cylinder will commence, air flowing from the receiver 6 through theinclined admission passages 8. The scavenging air then enters thecylinder through each of the elongated ports as 'above described, andthe air flowing from any port adjacent to the central wall 14 will bedeflected by the tangential speed component Y of the air flowing throughthe port 'or ports more remote from the central wall 14, the internalcurvature of the cylinder serving to guide the air flowing from thoseports which are remote from the central wall. In this way the scavengingair will be directed upwards against the inner surface of the cylinderabove the admission ports, i. e, on that side of the cylinder oppositeto the exhaust ports, the air from both sets of admission ports thenflowing towards the cylinder head substantially as shown by the arrows15 in Figure 1. The upward current of air 2 will tend to prevent thatentering through the ports adjacent to the central wall 14 from passing110 diametrically across the cylinder and escaping through the exhaustports without taking part in the scavenging operation.

By arranging the admission ports and passages as shown in Figure4 inwhich all the ports extend in similar spiral directions and theinclination of all the walls of the passages leading to the portsissimilar, the air will be caused to flow around the inner surface ofthe cylinder and to rotate about the cylinder axis on its way towardsthe cylinder head.

The invention may be applied with advantage to double-acting two-strokeengines as illustrated in Figure 5, since in engines of this type theoverall height is necessarily restricted with a consequent restrictionof the dimensions of the scavenging air ports, which may make it amatter of some difliculty to obtain effective scavenging of all parts ofthe cylinder. By providing ports in accordance with'the inventionhowever this diificulty is overcome even when the dead centre of thepiston lies in the radial plane be- 'tween the two halves of thecylinder.

It will be seen that with a cylinder having admission ports arranged inaccordance with the present invention that part of the combustionchamber above the admission ports is swept by an upward current of freshair flowing at high speed, i

and that the escape of scavenging air directly across the cylinder tothe exhaust ports is reduced to a minimum.

The constructions above described are given by way of example only anddetails may be modified without departing from the spirit of theinvention. For example the spiral directions in which the admissionports extend and the inclination of the passages leading to these portsmay be .lar.

air at a pressure difl'erent from that of the air supplied to theremaining ports:

I claim: a

1. In a cylinder for two-stroke internal combustion engines thecombination with the piston of admission and exhaust ports controlled bythe piston, the admission ports being arranged in the cylinder wallsubstantially opposite to the exhaust ports and a series of admissionpassages terminating in elongated ports in. the cylinder wall, thelength of eachport extending in a spiral direction in the cylinder wall,the passages being so inclined that the air enters the cylinder througheach port along a path which, when projected on to the cylinder wall,lies in a direction substantially at right angles to the length of theport.

2. In a cylinder as claimed in claim 1 the arrangement, that at leastsome of the ports and the passages leading thereto are inclined in adirection different from that in which others are directed so that theair enters the cylinder from some of the ports along paths each orwhich, when projected on to the cylinder wall, lies at a substantialangle to the paths of the air enter- 100 ing the cylinder from the otherports.

3. Ina cylinder as claimed in claim 1 the arrangement, that all theports extend in similar spiral directions and the inclination of all thewalls of the passages leading to the ports is simi- 105 4. In a cylinderas claimed in claim 1 the arrangement, that the walls of the passageleading to each admission port from an angle of between 30, and 45 witha plane tangential to the cylinder.

5. A two-stroke internal combustion engine cylinder, having admissionports and passages leading thereto as claimed in claim 1, in which thereis also, an air supply conduit or chamber communicating with theadmission ports, and one or more non-return valves for controlling theflow of air between the chamber and the admission ports, the latterbeing so arranged that they begin to be uncovered by the piston beforesame begins to uncover the exhaust ports.

CHARLES SCHAER.

